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Full text of "Text Book Of Mechanical Engineering"

Appendix II.

827

cause being the sudden arrest of the accumulator  weight and
consequent absorption of inertia.

^ P-.330. Electric Welding.—There are four systems at
present in use, the Thompson, Benardos, Zerener, and Voltex.
The first is useful for wires or bars, heat being caused by their
resistance, while the Benardos uses the arc, and is suitable for
repairs generally, but both require large installations. The
Zerener process avoids passing the current through the material,
the arc between two carbons placed in line being deflected upon
the work by means of electro-magnets. The Voltex system also
adopts two carbons; but they are set mutually at about 45°, and
magnets are unnecessary. Both the last-named systems are self-
contained, being carried about with ease, and it is claimed that
there is a saving in current of 30 % in the Voltex over the Benardos
process. Also that the double carbon apparatus does not harden
the parts so as to prevent machining, as in the other cases. The
Voltex requires a current of 80 volts, with 120 amperes for
welding, with 30 amperes for brazing, and with 5 amperes for
soldering. (Seep. 1.055.)

P. 332.    Setting for a Lancashire Boiler.—This type
of boiler not being complete without external flues, which also

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act as boiler supports, sections have been shewn in Fig.  797.
The direction of draught is indicated by arrows:  through the